Phospholipase A is an enzyme catalyzing the hydrolysis of the acyl linkage of glycerophospholipid and includes phospholipase A.sub.1 catalyzing the hydrolysis of 1-ester linkage of glycerophospholipid and phospholipase A.sub.2 catalyzing that of 2-ester linkage thereof. Although both of the phospholipases are widely distributed in the biological world, they have recently been noted from the standpoint of their connection to various diseases.
For example, in ischemic diseases such as cardiac infarction, it is believed that phospholipase is activated to disintegrate membrane phospholipid, giving an increased infarct size. Furthermore, studies have been made on the connection of the phospholipase to other various troubles.
Under these circumstances, various phospholipase A.sub.2 inhibitors have been proposed from the standpoint that the inhibition of phospholipase, particularly phospholipase A.sub.2 (PLA.sub.2) is effective in the prevention and treatment of various diseases (see Japanese Patent Laid-Open Nos. 255,749/1985, 175,466/1987, 2,968/1988 and 258,854/1988).
The inventors of the present invention have eagerly studied for many years on substances which can inhibit phospholipase A.sub.2 to find out that a benzenesulfonamide derivative or a pharmacologically acceptable salt thereof which will be described below exhibits a high inhibitory activity against phospholipase A2 and therefore is useful in the prevention and treatment of various diseases, for example, ischemic diseases such as cardiac infarction. The present invention has been accomplished on the basis of this finding.